RS3M is a great choice! I guess depending on where you're buying your cube from, I'd suggest just buying lube anyway, but I don't think you need to get too much into it. There are different lubes for core vs pieces and many different types/feels but I think just buy one for the pieces that can make it feel smoother. That's a huge, quick help in making your cube feel better.

Hi all… I’m old (42), and achieved the life goal of learning to solve a cube. Then I got a 2x2, 4x4, and a 5x5 front the wife for mother’s day. Got them fairly figured out (haven’t memorized the 4x4 parity algs, I’ll admit).

Hi. Welcome!

I’m about the same age, but I’ve this achievement unlocked since my 20s. Fast-forward 10 years later where I took interest in the cube again.

Trying to figure out what’s next. Getting fast w a 3x3 is probably it…

That’s one way you can take (Sub-60 sub-45 and sub-30 are quite reasonable goals for us oldies). Then there is other exponents (but you have already begun. Then other "WCA cubes" like pyraminx, skewb, square-1… Then other weird cubes (cuboid, bandaged…). And you can also explore different methods, blind (that’s not really that hard if you don’t expect a sub-60 solve, but rather expect to solve a cube blind (~5 to 7min for a total beginner like me), FMC… That’s what I love with ~~cubes~~ twisty puzzles. There is so many way to play with it.

If I get a speed cube (looking at an RS3 M 2020), should I be concerned with things like lubes at this point, or should I just get one and go?

I don’t have any and don’t think that it will change a lot of my cubing experience/times if I have a well-lubed cube. But it’s relatively cheap so if you think you’ll become "serious" about cubing, yes!